Process for lapping gauge blocks



F. c. WEAVER PROCESS FOR LA PPING GAUGE BLOCKS Original Filed Jan. 17,1922 June 23, 1925. I 1,543,041

4?"- /8 9 l a Ag y l8 V 1 7 1b Z I I s a" 2 "Anew/2 Patented June 23,1925.

UNITED "STATES FLOYD c. WEAVER, or WASHING-TON, nisrnlor or COLUMBIA.

PR'ceEss on LAIPPING AUGnBLoeKs.

original application filed January 17,19easena1 No. 530,001

Patent Ne. 1,476,863, dated December 11, 1923." Divided andthisapplication filed September 6, 192 seri rire. 586,521.

To" all whom it may concern:

Be it known that I, -FLOYD :VVEAVER, a citlzen of the United States,residing at Washington, Districtof Columbia, have in:

vented certain new and useful Improvements in Processes for LappingGauge Blocks, of which the following is a specifi: cation, referencefbeing had therein to the accompanying drawings. r i

This invention relates to a process for making-precision trueplanesurfaces, and the object of the invention is the production ofprecision true planes or true plane surfaces, and also of precisiontrueplane sur faces precisely parallelto each other and at a given ordesignatedseparation" from each other for any deslrable or practicalmaterial, such as glass, metal, natural 'crys tals, etcetera, thesurfaces to be plane and parallel to optical interference testing -ac-'curacy This application is'a divisional case, of my application, filedJanuary 17, 1922, Serial No. 530,007, upon which U. S. Patent No1,476,863 issued on December 11,- 192a 7 I With the foregoing and otherobjects in view, -my invention comprises, certain novel combinat ons,constructions and1-arrangements of parts as will be hereinafterdescribed, illustrated in the accompanying drawings, and moreparticularly pointed out in the appended claim. J 1 v In the drawings: lI Figure 1 is a fragmentary, transverse, sectional view through one form,of' a lapping machine used in rough lapping processes. 1

Figure 2 is afragmentary, transverse,

' sectional view through the machine partly illustrated in Fig. 1', withcertain mechanical parts removed to permit the device to ac-' commodatethe final lapping process.-

Figure 3 is a transverse, sectional view of the machine as employed forthe purpose of lapping spheres. V s Figure 4: 's a fragmentary plan viewof, a part of the lapping machine, illustrating the manner in whichcylinders are mounted upon the device when they are to be lapped;

Figure 5 is a fragmentaryplan view- 0 the device illustrated in Fig. 3.I

; Inasmuch as my machines for performingtlie processes are fullydescribed in my SJ application, Serial No. 530,007, filed Jan-- uar'y17,1922, up0niwhich U. S. Patent No, 1,476,863 issued reference can behadto said patent, as it is only necessary todescribe the following aprecisionmechanical'to 0.0002v over nominal size 'of the'gauge blocks,et cetera. I

The first sizing operation is done on the equipment shown in Fig; 1,where the gauge blocks 10 are mounted in perforations of the thin plate14; operatedby the driving or r strokepin 13, and moved between the twovindependent plates ll and 1.. The master plate 1 is mounted upon; thework carrying plate 2 andis rotated automatically or at the will of theoperator, while the lapping plate 11 is lowered by the progress of the'lapping'o'f the ends of the gauge blocks 10 until the carrying ringplate 18 rests upon the limitingor stopiring 1,7, which is pre- 1viously adjustedfor afixed height or length of the secondary standardorhgaugebloeli 16 or some desired final length or height of the, gaugeblocks 10. ,Thus'thejlapping proceeds until the lapping pla'te ll, whichis? rigidly attached to the carrying ring plate 18 by means o'fring 19,,comes to the limiting position denoted bythe position of the stop ring17, Uponcompletionof the lapping, the lapping plate 11 is lifted offto-' gether with the thin plate 14, after the driv ing or stroke pin 13is removed, thus leaving the gauge blocks 10 then rough sized to.

000005" on top ofthemasterplate 1, which are the-n taken off and cleanedforinsp'ection' and preliminary measurements. 7 1 V I The second orprecision lapping operation is doneon the machine shown inFig. 2. Thegauge'blocks 10, after sizing operation, are carefully set in intim'atecontact on the master'plate 1, i. e., by wringing, and the spacesvbetween the gauge blocks and the metal ring Q tare filled with hard waxor resin 24* nearly to the level ofQthe top edge of the ring 24 and thentheexposed surface is proof coated to resist action of liquids carryingthe lapping abrasives, s'uch as lime water, gasohneand OllS, benzols, etcetera;

After this-wax or resin 24-has hardened wedges 35* are carefullyplacedat symmete rical intervals, thus securing the ring 24 and thegauge blocks 10 in the bed of wax or resin to the auxiliary ring 3,preventing displacement of the gauge blocks during the lapping process.Precaution is to be taken to insure the cleanliness of the lappingsurface of the lapping plate 11 before putting the plate in position ontop of the gauge blocks 10. With the lapping plate 11 thus in place andthe stop ring 17 set for the proper value according to the secondary thepin 13, which is connected to suitable power sources, the master plate 1fastened to either automatically or at the will ofthe operator. Thus thetop faces of the gauge blocks 10 are re'duced by the lapping effort ofthe plate 11 until the carrying ring plate 26 (see my prior Patent No.1556,8633) engages the stop ring 17, when the operation is completed.The stop ring 17 is set for the first surface to lap off approximately0.000020" of the excess stock left by the first sizing operation, i. e.,0.000050. Thus there is left approximately 0000030 for the second partof the precision lapping operation. H

The second part of the precision lapping operation consists in removingthe lapping plate 11 with thecarrying ring plate 26 and the ring 19, aswell as the stop ring Y17 and the sleeves 8 and the studs 20 and nuts 21and 22 of said patent. After the wedges 35 are removed, the metal ring24- is given a sharp rap with a hammer on the end of a soft wood blockheld tightly against the edge in a parallel plane to the surface of themaster plate 1. This sharp blow causes no harm and is enough to startthe ring 24: and

the-mass of wax or resin and gauge blocks 10 loose from the surface ofthe master plate 1. In cases where all the gauge blocks 10 do not comeoff readily the wax or resin is dissolved or chipped off and the gauge 7blocks, slightly warmed, are then removed one at a time Care isnecessary at all times to preserve the surface of the master plate 1from any injury, as its surface is kept in perfect condition as theprimary reference surface, both of this process operation and thesucceeding ones. v V

After removal of the gauge blocks '1 with all parts, and the surface ofmaster plate 1 is thoroughly cleaned, the gauge blo ks are reset withthis last precision lapped surface down on the master plate 1, in thesame manner as above described for the first precision lapped surface.The lapping then proceeds in the same way after replacing the stop ring17 and the other rings associated therewith, thelapping plate 11 and thepin 13 in position as for the first 7 surface, and graduated nuts 22(see my Patent No. 1,476,863) are set for the final tolerance or excessstock amount, i. e., which should be approximately 0.00002". That is,this last operation of the precision operation should take approximately0.00001 from the previously remaining 000003 and thus leaving the0.00002 for the following final operation. The gauge blocks 10 are againremoved as beforeand are'clean'edfor inspections and tests. Thus thegauge blocks are ready for the final perfecting lapping and opticalpolishing stage.

The perfecting lapping and the optical polishing process is done on themachine shown in Fig. 2, where the gauge blocks 10, lapped in thepreceding process to within 0.000020 over size, are now carefully set orwrung on th masterplat'e 1. The stop ring 17, the studs 20, the nuts 21and 22, .the sleeves 8, (see my Patent No; 1,476,863) the carrying ringplate 18 and the ring 19 are all removed, leaving the lapping plate 11free for stroking by the pin 13 over the top surfaces of the gaugeblocks 10 for either the lapping or polishing. In the final lapping asuitable abrasive medium is fed through the vents 23 in the lappingplate 11 to the gauge blocks'10. The lapping in this precision stage isagain only onone surface at one time. This first lapping stage isintended for the removal of approximately 0.000010, with very frequenttests by optical flat and standard gauge set on the extending portion ofthe master plate 1 beyond the ring 24.jthu's readily and preciselyfollowing the dimensional progress of the work.

Following this lapping operation where the highest finish is secured theoptical polishing is proceeded with in a similar manner. The lappingplate 11' is coated on the lapping surface with a polishing pad of waxor pitch made flat against a plane master surface while still plasticfrom heating and then allowed to cool. This surface is then out bygrooves making a checked pattern as is done for the metal lapping plate11 and vents 23. In operation the plate 11 with its polishing pad andpolishing compound are worked by stroke pin over the top surfaces of thegauge blocks 10 in precisely the same manner as for the lappingoperations. The master plate 1 on-the carrying plate 2' is eitherrotated automatically or at the will of the operator. Upon completion ofthis top surface of the gauge blocks 10 with an optical polish andanswering the interference tests for flatness the gauge blocks 10 arethen removed as heretofore described and then reset upon plate llwiththe polished surface wrung on the top surfac of band 24: et cetera andthe wedges 35 the lapping of the last face of-the gauge blocks 10 isbegun. The gauge blocks 10 at this stage have approximately 0.000010 tobe removed. The lapping plate 11 is first given a seriesof symmetricalstroking movements by pin 13 and then, the gauge blocks are carefullytested after removing the lapping plate 11 by an optical master flatsurface and a standard gauge set upon-the extending portion of themaster plate 1 beyond the ring 24:. Thus the exact dimensional or lengthchart is made of the gauge blocks 10, showing which portion" of thewhole is the highest and where greater lapping is necessary to bring allthe gauge blocks 10 to precisely the same length. In.

case of a section of th gauge blocks 10 having a greater length thecenter of the lapping plate 11 is shifted/co have a series of shortcircular or elliptical strokes over the particular high portions, whichis accomfinal size.

plished by operating master plate 1 to bring these high portions at willto a point of maximum lapping effort. Thus by following each measuredperiod of lapping effort of the lapping plate 11 by testing with anoptical master surface and the standard gauge as above described gaugeblocks 10 can be brought down step by step to the final value, which inpractice means this last lapping and correcting should be car.- riedapproximately to within 0.00003 of With the completion of thisperfecting stage of lapping, the gauge blocks 10 are now given anoptical polish as above described for the first surface. During theprogress of the polishing frequent tests with the optical master surfaceand standard gauge will prevent in some cases excessive polishing andthe reduction of the remaining stock or more than the 0.00003. Generally this polishing can be carried to within 0.00002 or less for finalsize, leaving the gauge blocks 10 optically polished, optically planesurfaced, optically plane parallel faced, and precisely the given lengthto within 0.00002" or less over nominal value, without any mar-ring of apreviously given finish to the now lapped faces or surfaces. Both glassand metal blocks 10 are worked in similar ways. The original setting ofthe blocks 10 is slightly different when the master plate 1 is made ofglass and when the gauge blocks 10 are glass and the resin between thegauge blocks 1 is replaced with plaster Paris of compounds which areprincipally calcium carbonate.

The process for lapping precision spheres and precision cylinders isdone upon the equipments or machines shown in Figs. .2 and 3. Thearrangements of the spheres 35, as shown in Figs. 3 and 5, with the-sys-' tem of movable concentric bands 29 are placed upon the masterplate 1 within the band 28, which is secured by wedges 35, 'as shown inFig. 3, and the lapping plate 11 is operated in'precisely the samemanner'as above described for the gauge blocks in Figs. 1, 2 and 3. Thelapping plate 11 is stroked by pin 13 and the-master plate 1 is rotatedeither automatically or at will of the operator. The first stages oflapping are accomplished on the machine shown'in Fig. 3, with-thelapping plate 11 secured to the carrying ring plate 26 by means of thering 19,-thus the lapping maybe continued until the ring plate 26 (seemy prior Patent No. 1,476,863) comes into contact with the stop ring 17set for the secondary standard or gauge'block 16 which in turndetermines the size of the spheres 35. After completion of this firststage of the lapping plate 11 can be removed and prepared for the finalperfe'cting'lapping as shown in Fig. 2, where all the operatingprocesses for the gauge blocks 10 are repeated for the spheres 35mounted as shown in Figs. 4 and 6. The diameters. of the spheres 35 aredirectly measured by an optical master surface and a standard gauge, asbefore described for the gauge blocks 10. Thus the size of the spheresis controlled as readily as in the case of the gauge blocks 10, due tothe principle of the two successive concentric ring bands 29 binding thespheres 35 at two points in addition to the point of contact of thespheres with the master plate 1, giving avice grip upon the spheres'asthe lap-' ping plate 11 is driven over the top contact of the spheres.The action of the lapping plate 11 bearing on the spheres 35 in thedirection of the movement of the lapping plate 11 or the relativemovement of the lapping plate 11 to the master plate 1. The concentricring bands 29 prevent or resist individual movement of the spheres 35,and the resulting composite effect of the rolling spheres is a crowdingof the ring bands together at points where the motion of the lappingplate 11 is in the direction of a radius of the bands, thus clamping thespheres between two successive bands and the lapping plate 11 removingthe high projecting portions of the spheres. The stroke pin 13 is givena series of symmetrical strokes to give a maximum lapping effort "to anormal direction.

as above described for spheres throughout, excepting that the pin 13 isgiven a principal' direction normal to the axis of the cylinders or at avarying small angle The parallel sided and hardened bars fitting looselyin notches in the bars. 32 perform the same function as the bands 29- inthe case of the spheres In operation the annular ring 81-7 in Fig. 5 andthe bars 82 are placed upon the master plate 1 and then the limitingouter band 28' is secured by Wedges 35, thesame as they retain the metalband 24 in Fig. 2, and the rectangular bars. 8% are dropped intotheirrespective notches in the ping surface of the plate 11 resting on theupper portions of the cylinders 30 and the stop ring 17 adjusted to thesecondary standard or gauge block 16 and the lapping operation is thenproceeded With in the manner herei-nbefore set forth for the gaugeblocks10.

.Vxlhat I claim is:

A process of the character described cont.- prlsing placing articles tobe ground: upon,

a suaaort havin a flat u oer article rece-iving face with: the-articlesheldin spaced relation toeach other and grinding-the upper ends ofthearticles, a; predeterm ned amount to preyide endfaces parallel; to the aarticle engaging face of; the support, then inverting the articles andplacing a Water-- proofed plastic about and, between the; an ticles tohold. the, articles. in, place, then grinding the previously Ling-round;ends of the articles to remoyea p-redjeternnined amount of material and:provide end faces,

parallel to the previously ground end fa.ces,,

removing the articles and plastic from the support and thoroughlycleansing the articles and subjecting the end faces thereof to a finalgrinding, to: reduce the articles toa desired size with their endfacesexactly fiat and parallel. to each other.

In testimony whereof I hereunto affix my signature.

FLO/YD 0., WEAVER.

